The present invention relates to a new and improved contruction of a helical surface-shaped machine part of the type comprising a flank profile or section extended in radial direction. This invention also relates to a method for manufacturing such machine part, the use of the machine part, and a component for performing the method.
Such machine parts or components are used, for instance, as conveyor elements (for example as Archimedes screws, conveying worms) but also as force transmission elements for the transmission of rotational moments about the axis of the helical surface between two shafts which are misaligned, in other words in the broader sense are used as helical springs which can be subjected to bending loads. A further application is for instance as coiled cooling fins at a pipe or tube, but this field of use is of lesser importance in the present situation since coiled or helical-shaped cooling fins are seldom subjected to considerable mechanical loads during operation.
Apart from the possibility of previously forging or casting and the subsequent machining from the complete part, a technique especially practiced with conveyor worms, there are two possibilities of producing such machine parts or components.
The first of these possibilities resides in winding a rod having a cross-section corresponding approximately to the flank profile or section while in an upright position thru a predetermined diameter, for instance about a winding mandrel. With this manufacturing technique the degree of the lengthwise extent of the rod section is extremely limited by the winding radius. In other words, it was not heretofore possible with the upright winding of a rod to produce such a machine part or component wherein the height of the flank section considerably exceeded the size of the winding radius. Of course, the permissible winding radii vary from material to material and also are dependent upon the cross-sectional shape of the starting profile. Since, however, as a general rule with such machine components it is especially the peripheral regions of the helical surface or the regions which are remote from the axis thereof which are exposed to mechanical load (for instance wear or bending about the section root) the material selection equally is governed by such criteria. Consequently, in particular flowable, i.e., easily cold workable material, which otherwise would allow for higher flank sections, cannot be used for these reasons.
The other mentioned possibility for manufacturing such machine components resides in initially preparing circular rings with a ring cross-section corresponding to the predetermined flank profile or section, then cutting open these circular rings for instance along a radius and deforming the same into a helical surface, whereafter a number of circular rings are connected in succession into the machine component with the cut locations abutting one another. While it is thereby possible to produce sections of practically random height, nonetheless not only is the manufacture thereof extremely cumbersome and difficult, but the finished product also is associated with drawbacks attributable to the manufacturing technique. Such drawbacks, in many instances, render completely unusable such type manufactured machine component. For instance, with this prior art technique it is practically not possible, during the manufacturing process, to maintain an exact size of the pitch and/or to prevent irregular mechanical properties attributable to the connection locations.